Shielded spabx-pluo



ocr'. 1o,- 19331 A 61M'. PAUL-son' s'nIELDspk-snnk PLUG VFiled spt. '4, 1930 INVENTOR RNE l!" Patented Oct. 10, 1933A:

UNITED STATES PATENT OFFICE;

The B. G. Corporation, poration of New York Application September 4,

New York, N. Y., a cor- 1930. semina. 419.684

. This invention relates to spark-plugs, and more especially to spark-plugs for aviation engines. The severe service conditions which are imposed on spark-plugs for airplane motors are familiar to those skilled in the art, as is also the importance of enclosing all parts of the hightension current-carrying system by a continuous metallic shield to prevent interference with the reception of signals by adjacent radio receiving sets, and also to protect the exposed parts of the ignition system from detriment by the elements or otherwise. 1

The object of this invention is to provide a spark-plug, and more especially ./a shielded spark-plug, thev construction of which is such as to prolong its life and to insure its effectiveness in such service, and to aiiord convenience, and which is economical to manufacture.

The invention comprises novel features of great utility in spark-plugs, andlnovel combinations of elements making. an improved sparkplug and an improved assemblage oi the sparkplug and its high-tenslorifconductor.

Further objects are to provide a shielded sparkplug of compact construction; to make it easy to remove and insert the conductor, and to establish the electrical connections; to guard against injury to insulation .parts of the spark-plug and conductor'as v'.the result of such operations; to lock the conductor securely against accidental withdrawal; to insure good electrical connection for the high-tension current to the plug, to the end that the spark-plug may not fail to function; to relieve the conductor shieldingy of strain and to insure -lts electrical connection with the body o! the spark-plug; to provide an improved terminal for detachably connecting the insulated high-tension conductor with the plug, in a socket of which the conductor is inserted; to provide a shielded spark-plug having a swiveled elbow through which the insulated conductor is passed and which has a terminal constructed 'to be slipped over the barrel ot the plug and to be locked thereto securely yet detachably, the same v construction providing a swivel which enables the elbow to be turned in any direction; to provide an insulating spacer tube on the portion of the conductor which is inserted in the sparkplug; to construct this spacer tube of mica and to reinforce it in a simple manner which adds enormously to its strength; to provide a sparkplug which is thoroughly insulated with mica: to protect the mica insulation from frayig and.other' injury; to provide a simple and very eiective reinforcement for a mica lining for the socket in which the conductor is inserted, this reinforcement serving also to lock the lining in place; and to provide oth/er improvements and advantageous combinations the nature of which will appear.

In the accompanying drawing forming part hereof:

Fig. 1 is a longitudinal section through a sparkplug embodying the improved construction, the plug being of the elbow type;

Fig. 2 is a cross-section taken on the 2-2 oi Fig. l;

Fig. 3 is a perspective view oi an insuiating spacer tube; and

Fig. 4 is an illustration of a straight-type plug ill embodying the improvements, the view being partly in elevation and partly in longitudinal section.

Figs. l and 2 will iirst be described.

The shell 2 is of conventional form, as is also fili the nut or bushing 3 screwed into the shell against a washer 4. A spindle 5 surrounded by rolled -mica insulation 6 and having a head 7 and an electrode 8, of conventional form, is gripped in the body of the plug so as to produce a gastight joint, in a known manner, by forcing a compressible metal ring 9 upward in a tapered opening of the nut. As is also customary, mica disc insulation 10 is conned between this ring and the head.

For the purpose of a shielded aviation sparkplug the metal body of the plug is provided with a barrel 1l which extends upward considerably above the upper end of the spindle to enclose the spindle and the electrical connection between the 00 samemndthe conductor which leads the hightension current to the spindle. This barrel is preferably in one piece with the nut, though that is not necessary in all cases.

'-I'he hollow interior of theV barrel is of consid- 95 erably larger diameter than the spindle and its insulating sleeve 6, and the barrel is lined throughout its length with a rolled mica sleeve 12, which is inserted from the upper end of the barrel.

.The upper end of the insulating sleeve 12 is bound by a ferrule 50 of U-section embracing the layers and pinched thereon. This ierrule is very effective for preventing traying oi.' the mica when the end of the insulated high-tension conductor 105 13 is inserted in or removed from the socket formed by the portion of the barrel and itsflinline " ing above the spindle. Furthermore, this ferrule is utilized to lock the sleeve 12 in the barrei against being drawn out with the conductor. For this im purpose the inner wall of the barrel is formed, at the upper end, with a circumferential recess 14 into which the ferrule is expanded.

'I'he space in the lower part of the barrel between the mica lsleeves 6 and 12 is occupied by a stack 15 ofl mica washers, this. stack bearing at its lower end against a inetalwasher 16, which in turn bears on a shoulder 17 of the body; 'A thin cup 18 and a heavy metal washer 19 overlie the mica disc insulation, and'the upper end of the spindle 5 passes through these'parts and is upset at 20 to secure the cup in place and'to confine the mica disc insulation under more or less compression. Also, in this way, the spindle, which can not move upward, by reason of the construction which has been described, is prevented from moving downward, and is, therefore, locked in the body.

'I'he special functions of the cup 18 will be described vlater on.l It and the washer 19 might be made in one piece were it not for manufacturing considerations.

The insulated conductor 13 is passed through a metal elbow 21, which has a swiveled, detachable connection with the barrel 11. A continuous braided metal sheath 22 covers all of the cable up to the elbow, to which it is connected. 'Ihe manner of securing the elbow to the' insulated conductor and electrically connecting it to the metal sheath may be varied. In the particular construction chosen for illustration, the' outer end of the elbow has a screw-threaded enlargement 23, formed with a tapered mouth in which a conical rubber washer 24 is seated. A flan ed collar 25 is soldered to the end of the sheathl 2 and bears against the washer 24, and a coupling nut 26 screws on the enlargement 23 to draw the collar againstgthe washer and squeeze the latter against its tapered seat and inward to clasp the insulation ofvthe conductor." Y

The inner end ofthe elbow 21 is soldered or otherwise secured inthe -narrow upper end of a terminal or coupling 27 designedfor quick mechanical and electrical connection and disconnectionwithreference to the barrel 11. The lower part of thisdetachable connection is large enough to slip over the barrel for a distance limited byI an internal shoulder 28 abutting the end of the barrel. I l

This partof -the detachable connection is slotted longitudinally to form numerous resilient fingers 29 to clasp the barrel. The latter has an external circumferential shoulder or recess 30 below itsupper end, andthe fingers have inbent regions 31 to engage under this shoulder, the engaging surfaces being inclined, however, to permit the nngers to yield and the connection or terminal 27 to be pulled of! the barrel when a longitudinally slidable,rigid, locking ring 32 is forced upward.

A similar detachable its locking ring are prior application, 16, 1929, but in of the fingers were directed outward and I have found that that madeit too diflicult'to push back the ring 32 to release the ngers 'and that in doing so the; mechanic was likely to injure'his hand on the ends ofthe ilngers.'v I now are each of the nngers gradually outward from-the inbent curve 31 to a rounded hump 33 and then turn the extreme end 34 inward ward but not in contact with the barrel. l

terminal conncun and disclosed and claimed in my Serial No. 378,611, filed July The ring.3il has la circular internal groove 35 curved transversely-to fit the humps 33. Whenv that application the extremitiesy the ring is forced downward so that the humps seat in this groove, the inbent portions 31 are positively locked with the shoulder 30, so that the connection can not be pulled on the barrel as long as the ring is in this position. 'Ihe ring is also strongly, though non-positively locked with the fingers. It can not be pushed downward from this position, because that would cause the inturned extremities of the fingers to dig against the barrel, but it can be forced upward without excessive eifort so as to permit the fingers to be pulled* away from the shoulder 30.

Another difference between the present elbow plug and the elbow plugs disclosed in my prior applications, Serial No. 378,221, tiled July 15, 1929, and Serial No. 378,611, filed July 16, 1929, is that in those plugs, the inner end of the elbow had a permanent swivel connection with the barrel, the detachable connection being at the outer end of the elbow. In the present plug, the insulated conductor is passed entirely through the elbow, and the detachable connection is between the inner end of the elbow and the barrel, and this detachable connection is itself the swivel which enables the elbow to be turned in any direction about the axis of the spark-plug proper.

A length of the insulated conductor 13 projects'below the terminal connection 27 to enter the socket of the barrel, lined by the mica sleeve 12. This portion ofthe conductor carries and is surrounded by a rolled mica tube 51 the opposite ends of which are bound by ferrules 36 and 37, similar to the ferrule which binds the upper end of the lining sleeve 12. These ferrules not only keep the ends of this insulating tube from fraying but also give it great strength as a compression member. strengthened by eyelets 52 securingA the layers of ymica together intermediate the'ends of the tube.

. This insulating tube acts as a' spacer to prevent the conductor being pulled out of the spark-plug when the connection 27 is in place. The upper end of the tube, protected by the ferrule 36 bears against an internal shoulder 38 of said connection, whilst the ferrule 37 is mechanically connected with the stranded wire 39 of the conducg tor, so that any pull on the conductor is taken in tension by the wire and applied by the ferrule 37 as an upward thrust through the tube 51 against `the detachable connection.

The ferrule 37 is accordingly preferably formed with an internal web 40 having a central opening. The strands of the conductor are passed through this opening and bent outward, and a headed screw or pin fastening 41 is inserted upward through the hole into the body of the conductor, where it 'spreads and firmly engages the strands of the conductor wire, laterally compressing the insulation 42 of the conductor. 4In this way a strong connection is secured.

- In this combination, the ferrule 37 constitutes `an embodiment of a tip piece connected to the 'conductor so as to apply pnessure to the spacer tube, and it may take other forms.

The head of the fastening 41 also serves to secure to the end oi' thev conductor the upper, small convolution oi' a conical contact spring 43, which l latter makes a sure electrical'connection with the spindle 5v when the conductor is pushed into the barrel.

The cup 18, lor the'washer 19 which may be regarded as part of the cup; forms a seat and an sleeve 12 from injuryby the spring. Further- 'Ihe tube may be further more, the wall of the cup is extended upward between the ferrule 37 and the sleeve 12, so that .the latter is saved from possible injury by lateral pressure of thisferrule or tip piece. A

The straight-connected plug shown in Fig. 4 is similar in construction to the elbow plug which has been described, except that the elbow is omitted and the shielding sheath 22 is connected directly to the detachable terminal connection 27. This may be accomplished by soldering or otherwise, but I have shown the sheath turned-back on itself over a ring 55, which is forced into the upper part of the terminal so as to bind the terminal frictionally to the cable and make a good electrical connection between the sheath and the terminal.

In my aforesaid prior applications there is disclosed a construction in which the insulated high tension conductor is inserted into amica-lined barrel of the spark-plug, and a mica tube is placed on this portion of the conductor so as to act as a spaced bearing at its upper end against a detachable connection or terminal and at its lower end receiving thrust from a washer or tip-piecefastened to the end of the conductor in the manner of the ferrule 31. As to claims herein directed to these matters the present application, therefore, refers back for priorily to those applications.

I claim: l

1. In a shielded spark-plug, the combination of an insulated spindle, a body in which said spindle is xed, a metal barrel extending from the body above the spindle to form a socket and part of the shielding of the plug, an insulated hightension conductor insertible into said socket to make electrical connection with said spindle, a metallic sheath about said conductor outside the spark-plug, a metal connection through whichv the insulated conductor is passed and to which said sheath is connected, said connection having detachable engagement with said barrel, a tip piece fastened to the conductor Wire, and an insulating sleeve about the portion of the insulated conductor within the socket, said sleeve acting as a spacer between said tip piece and said detachable connection.

2. In a shielded spark-plug, the combination of an insulated spindle, a body in which said spindle is fixed, a metal barrel vextending from the body above the spindle to form a socket and part of the shielding of the plug, an insulated high-tension conducfor insertible into said socket to make electrical connection with said spindle, a metallic sheath about said conductor outside the sparkplug, a metal connection through which the insulated conductoris passed and to which said sheath is connected, said connection having den tachable engagement with said barrel, a tip piece fastened to the conductor wire, and an insulating sleeve about the portion of the insulated conductor within the socket, said sleeve being formed of rolled mica and acting asa spacer between said tip piece and said detachable connection.

3. In a shielded spark-plug, the combination of an insulated spindle, a body in which said spindle is xed, a metal barrel extending from the body above the spindle to form a socket, a mica sleeve lining said barrel, an insulated high-tension conductor insertible into said socket to make electrical connection with said spindle, a metallic sheath about said conductor outside the sparkplug, a metal connection through which the insulated conductor is passed and to which said sheath is connected, said connection having detachable engagement with said barrel, a tip piece fastened to the conductor wire, and an insulating sleeve about the portion of the insulated conductor within the socket, said sleeve being formed of rolled mica and acting as a spacer between said tip piece and said detachable connection.

4. In a spark-plug having a body the outer portion of which forms a socket for the insertion of an insulated high-tension conductor and a connection through which the conductor is passed and which has detachable engagement with the body, a mica spacer tube surrounding the portion of the insulated conductor within the socket, and a tip piece mechanically connected to the conductor wire, said mica tube extending as a thrust spacer between said tip piece and said detachable connection.

5. In a spark-plug having a body the outer portion of which forms a socket for the insertion of an insulated high-tension conductor and a connection through which the conductor is passed and which has detachable engagement with the body, a mica spacer tube surrounding the portion of the insulated conductor within the socket, a tip piece at the end of the conductor, and a fastening for said tip piece penetrating lengthwise of the conductor in engagement with the conductor wire, said tube extending as a thrust spacer between said tip piece and said detachable coml nection.

6. In a spark-plug having a body the outer portion of which forms a socket for the insertion of an insulated high-tension conductor and a connection through which the conductor ris passed and which has detachable engagement with the body, a mica spacer tube surrounding the portion of the insulated conductor within the socket, and ferrules binding the ends of said tube, the lower of said ferrules being mechanically connected with the conductor wire, and the upper ferrule bearing against said detachable connection.

'7. In a spark-plug having al body the outer portion of which forms a socket for the insertion of an insulated high-tension conductor and a connection' through which the conductor is passed y and which has detachable engagement with thev body, a mica spacer tube surrounding the portion of the insulated conductor within the socket and bearing at its upper end against said detachable connection, a ferrule binding the lower end of said tube and having an internal apertured web, and a fastening passed through the aperture of said web into the conductor.

8. In a spark-plug having a body having a barrel forming a socket for the insertion of an insulated high-tension conductor, a mica sleeve lining said barrel, and a metal binding clasping the upper end of said sleeve.

9. In' a spark-plug, a body having a forming a socket for the insertion of an insulated high-tension conductor, the upper end of said barrel being formed with an internal recess, a mica sleeve lining said barrel,l a d a metal binding cla'sping the upper end o/fgtsaid sleeve and locked in engagement with said/recess.

10,-A spark-plug comprising thev combination of a central insulated spindle, a body having a barrel extending above said spindle to form a socket for insertion of an insulated high-tension conductor, an insulating sleeve lining said barrel, a spring to form electrical connection between the end of theconductor and said spindle, and a cup on the upper end of the spindle forming a seatfor said spring to protect the insulating lining of the barrel.

11. A spark-plug comprising the combination barrel i of a central spindle, a mica sleeve about said spindle, a body in which the spindle and its mica sleeve are fixed, a barrel extending upward from said body above the spindle to form a socket for the insertion of an insulated high-tension conductor, a mica sleeve lining said barrel, a stack o! mica washers occupying the space between said mica sleeves and bearing on a shoulder of the body, and means on the upper end of the spindle confining said stack.

12. A spark-plug comprising the combination of a central spindle, a mica sleeve about said spindle, a body in which the spindle and its mica sleeve are ilxed, a barrel extending upward from said body above the spindle to form a socket yfor the insertion of an insulated high-tension conductor, a mica sleeve lining'said barrel, a stack of mica washers occupying the space between said mica sleeves and 'bearing on' a shoulder of the body, and a conilning element bearing on the top of 'said stack, upper end of the spindle passing through said' confining element and being upset thereon.

' 13. SA` spark-plugV comprising the combination of acentral spindle-ja mica'- sleeve about said spindle, a b'ody inwhich .the spindle and its mica sleeve are ilxed, a barrel extending-upward from said body abovethe' spindle toi'orm a socket'for the insertion oi an insulated high-tension .conductor, a spring to 'form electrical connection between the end ofthe conductor and said'spindle,

a mica sleeve lining'said barrel, a.v stack o! mica washers' occupying-the space between said mica sleeves. and a cup on top of said stack forming'a seat for said spring to protect the mica lining ofthe barrel, the upper end of said spindle passing through said cup and'beingv upset'to secure the cup in place and to hold said stack' of washers in confinement.'

14. A spark-plug comprising the combination of a' central. spindle. a body having a barrel extending abovev said spindle to form a ,socket for insertion oi' an'v insulated high-tension conductor, 'a connection through which the conductor is passed and which has detachable engagement withsaidbarrel, an insulating sleeve vlining said barrel, an insulating spacer tube on the portion of the insulated conductor within the socket, said spacer tube bearing'at its upper end against said detachable connection, a metal binding clasping the lower end of said spacer tube andy connected with theconductor wire, a spring to form electrical connection between the conductor andthe spindle, and a cup onthe upper end of the spindle forming a seat for said spring,

the wall of said cup extending upward between vsaid metal binding and the insulating lining of .the barrel.

15. In a spark-plug having a body they outer portion of whichtorms a socket for the .insertion of an insulated high-tension conductor and a connection through which the conductor is passed and which has detachable engagement with the body, a mica spacer tube surrounding the porthe barrel. Y

tion of the insulated conductor within the socket and bearing at its upper end against said detachable connection, a ferrule binding the lower end of said tube and having an internal apertured web, a fastening passed through the aperture of said web into the conductor, and a contact spring secured to the conductor by said fastening.

16. In a spark-plug, the combination of a body containing an insulated spindle and having a barrel extending above the spindle to form a socket, an insulated high-tension conductor having a flexible metal sheath, a metal elbow through which said conductor is passed and to the outer arm of which said sheath is electrically connected, the end of the insulated conductor being insertedin said socket to make electrical connection with the spindle, said barrel having a circumferential shoulder, and a terminal on the inner end of said elbow having resilient lingers locking detachably with said shoulder and torming a swivel connection between the elbow and .17. In a spark plug having a body formed with a circumferential shoulder, aterminal connection adapted to be slipped over the end of said -bodywsaid connection having a plurality oi resilie'nt lingers formed with inbent regions to engage under said shoulder, each nger iiaring outward from -its inbent region to a hump and havingits extremity turned inward, and a rigid' locking ring encircling said lingers and movable lengthwisethereof to lock said inbent regions with said shoulder, said ring having an internal groove to lock with said humps, from which the ring can be forced vin, one direction to permit the lingers to be withdrawn from the body.

. 18.` In a spark-plughaving a body and a central spindle insulated from the body, the combination of a metal barrel with insulation lining extendingu'pward from the body above the upper end of the spindle to provide a socket for the insertion o! an'insulated high-tension conductor into electrical connection with said spindle, a connection through which the conductor is passed and which has detachable connection with said barrel, andan insulating spacer tube about the portion of the insulated conductor within said socket, said tube beingconnected to the conductor and var ranged to bear at its upper end against said connection.

19. In a spark-plug, in whichthere is a body, a central spindle insulated from the body, anda metal barrel extending upward from the body above the upper end of the spindle to provide a socket for the insertion oi' an insulated hightension conductor, a rolled mica sleeve lining said barrel, and a lock for said sleeve at the upper end ofthe barrel, said lock comprising a thin metal element bent over the upper edge of said mica sleeve so as to clasp its layers and protect the sleeve when the conductor is inserted and removed.

^ GEORGE M. PAULSON.

biscLAlMER Gam 41m 27, 1940,1 n

M.Pl.'lsm,v N ewxYork, N. Y. `Samnaun Y.SPARK-PLUG.' atoi 6 tobel l0, 1933. Disclaimer filed July 30 1940, by the assignee,

Patent 

